1. Field of the Invention
This invention is related in general to the field of data storage systems. In particular, the invention consists of a system for releasing log-in port resources.
2. Description of the Prior Art
Complex digital data storage systems typically include a high-capacity disk array, such as a redundant array of inexpensive/independent disks (“RAID”), for storing information. These data storage systems may utilize one or more data storage servers consisting of multiple processing clusters (“cluster”) to allow a plurality of host servers (“hosts”) access to the disk array. These hosts typically include input/ouput (“I/O”) adapters for communicating with other I/O adapters located at the clusters. Information may be transported over a Fibre channel transport layer, sometimes referred to as a fabric.
Two protocols used to communicate over the transport layer are Fibre Channel Protocol (“FCP”) and Fibre Connectivity (“FICON”). Each I/O adapter located at a host may be configured as either an FCP or FICON port. Typically, each port is allowed to access each other port connected to the fabric. However, zoning may be implemented on the fabric to segregate ports into sets, limiting which ports are allowed access to each other. Limiting which cluster I/O ports that a host port may access is referred to as fabric zoning.
A host port logs-in to a cluster by requesting log-in resources from a controller. The log-in resources typically include an area of memory within a memory device, such as a random access memory (“RAM”), for storing information about the host port. A log-in may occur at one or more level of the host's communication protocol. Low layer connections may include physical, data link, network, and transport layer connections as defined by the Organization for Standardization (“ISO”) in the OSI model. Upper layer connections may include application, presentation, or session layers. However, these layers may be considered either low layer or upper layer connections, depending on the needs of the user. A link-layer or transport layer log-in (“PLOGI”) may occur using either FCP or FICON. An explicit upper layer log-in using FICON is referred to as Establish Logical Path (“ELP”), while an explicit upper layer log-in using FCP is referred to as a Process Login (“PRLI”). Once logged-in, a host may request structured memory space within the RAID from the cluster. If the cluster grants the request, the host is deemed to be configured.
A problem may occur if a data storage server is on a fabric that is not configured to use zoning. Without zoning, numerous log-in requests to the same cluster may result in exhaustion of the clusters log-in resources, preventing other hosts from being able to log-in. While some hosts may be able to log into other clusters, a configured host will lose access to its structured memory if denied access to its granting cluster. Accordingly, it is desirable to have a system for releasing log-in port resources so that a configured host may log-in to its granting cluster so as to maintain access to its structured memory.
One solution is to temporarily take the cluster port off-line. While taking the cluster port off-line, any hosts logged-in to the cluster may be logged-off. Another solution is to manually disconnect the cluster port from the fabric. In this scenario, all hosts currently logged-in to the cluster will be disconnected without notification. Either way, the hosts lose access to the disk array through the cluster. Additionally, under fibre channel protocols, all tasks in progress during log-off are terminated. Once the cluster port is brought back online or reconnected, each host will have to log-in again. However, the problem will re-occur if all configured hosts do not log-in before the cluster log-in resources are exhausted again. Accordingly, it is desirable to free up cluster log-in resources without taking the cluster port offline or physically disconnecting it.